The issue numbers in commit messages like "Fix #_102 refs #_13 @30m" will be recognized by both Redmine (issues 102 and 13) and GitHub (issues 102 and 13).

GitHub have additional format for issue autolinks, but still the issue numbers in commit messages like "Fix GH-102 refs #_13 @30m" will be recognized by both Redmine (issue 13) and GitHub (issues 102 and 13).

If Redmine would have additional formats for issue autolinks, then commits like "Fix GH-102 refs issue#13 @30m" will be recognized properly by both Redmine (issue 13) and GitHub (issue 102), so described use case will get a chance to live.